1. Field of the Invention
The invention relates to storage-stable isocyanurate polyol dispersions. More particularly, the invention relates to storage-stable tris(hydroxyalkyl)isocyanurate polyol dispersions containing
(a) from 2 to 70 parts by weight tris(hydroxyalkyl)isocyanurate, PA0 (b) from 98 to 30 parts by weight of at least one polyol having a functionality of from 2 to 8 and a hydroxyl number of from 20 to 1800 and, PA0 (c) from 0 to 20 parts by weight, preferably 0 to 5 parts by weight of one or more dispersion stabilizers. PA0 (a) from 2 to 70 parts by weight, preferably from 10 to 40 parts by weight, tris(hydroxyalkyl)isocyanurate, in particular tris(hydroxyethyl)isocyanurate, PA0 (b) 98 to 30 parts by weight, preferably 90 to 60 parts by weight of at least one polyol having a functionality of from 2 to 8 and a hydroxyl number of from 20 to 1800, and PA0 (c) from 0 to 20 parts by weight, preferably from 0 to 5 parts by weight, of one or more dispersion stabilizers. PA0 (c1) silicic acids and silicates PA0 (c2) salts, preferably alkali metal salts such as sodium or potassium salts, and ammonium salts of perfluorated alkyl carboxylic acids having from 4 to 20, preferably from 8 to 18 carbon atoms, salts of alkyl sulfonic acids or perfluorated alkyl sulfonic acids having from 4 to 20, preferably from 8 to 18 carbon atoms, as well as perfluorated polyether polyols having molecular weights from 300 to 6000, preferably from 500 to 4000, and/or PA0 (c3) salts of fatty alcohol sulfates having from 6 to 30, preferably from 8 to 22 carbon atoms.
2. Prior Art
Tris(2-hydroxyalkyl)isocyanurates and a process for their preparation are described in U.S. Pat. No. 3,088,948. The products are nearly insoluble in polyols and organic polyisocyanates at the processing temperatures used for the preparation of polyurethane plastics, in particular polyurethane foams, and therefore are not suitable as starting components for such applications.
However, in order to use tris(hydroxyalkyl)isocyanurates, in particular tris(2-hydroxyethyl)isocyanurate as starting components for polyurethane plastics, specified amounts of solvents or solubilizing agents are added to the polyurethane formulations. This means, though, that such systems can only be used as binders for coatings or paints.
Since it is known that tris(hydroxyethyl)isocyanurate provides polyurethane coatings with a good resistance to weathering and increases their flame resistance, there have been attempts to put the products into a more soluble form through suitable modifications.
In U.S. Pat. No. 3,730,923 the tris(2-hydroxyalkyl)isocyanurates are oxyalkylated with ethylene oxide, 1,2-propylene oxide, or 1,2-butylene oxide and the resulting tris(2-hydroxyalkyl)isocyanurate-alkylene oxide adducts are processed with organic polyisocyanates in the presence of blowing agents and catalysts to form polyurethane foams having improved characteristics.
U.S. Pat. No. 3,174,950 describes another possible way of improving the compatibility with polyols. This method consists of preparing the isocyanate-group-containing prepolymers from diphenylmethane diisocyanates and tris(2-hydroxyethyl isocyanurate) in organic solvents. The disadvantage of this process is that the modification results in additional equipment and process costs, that the properties of the tris(2-hydroxyalkyl)isocyanurates can be changed in an undesired manner, whereby particularly flame resistance is adversely affected, and that the range of possible final product characteristics is limited.
The subject of European Pat. No. 04 116 is a process for the preparation of cross-linked, dense or cellular polyurethane elastomers through the reaction of polyisocyanates with one or more polyols, whereby tris(.beta.-hydroxypropyl)isocyanurate or its ethoxylated derivatives are used as a polyol component. The resulting elastomers may be cellular and can be prepared in a one-shot or in a prepolymer process at temperatures from 75.degree. to 150.degree. C., whereby the starting components are mixed together and then immediately reacted or an isocyanate-group-containing prepolymer is prepared from the polyisocyanate, high molecular weight polyol, and, in some cases, tris(.beta.-hydroxypropyl)isocyanurate, and this prepolymer is then reacted with the remaining starting components. The polyol mixtures cited in the patent are not storage stable at room temperature. The publication does not teach how the polyol mixtures can be stabilized so that even after several weeks of storage they are only suitable for two-component processing.